Use of EFG (Edge-defined Film-fed Growth) technique to grow a flat-plate-shaped Ga2O3 single crystal is known as a conventional method (see, e.g., PTL 1).
In PTL 1, SiO2 is used as a dopant material to introduce Si into a Ga2O3 single crystal. Since SiO2 has a small melting point difference from the Ga2O3 and has a low vapor pressure at a growth temperature of the Ga2O3 single crystal (at a melting point of a raw material of the Ga2O3 single crystal), it is easy to control the amount of dopant in the Ga2O3 single crystal.
Meanwhile, use of FZ (Floating Zone) technique to grow a column-shaped β-Ga2O3-based single crystal is also known as a conventional method (see, e.g., PTL 2).
In PTL 2, Si, Sn, Zr, Hf or Ge, etc., used as a thermally meltable control additive are added to a β-Ga2O3-based single crystal. Addition of the thermally meltable control additive increases infrared absorption properties of the β-Ga2O3-based single crystal and causes the β-Ga2O3-based single crystal to efficiently absorb infrared light from a light source of a FZ apparatus. Thus, even in a β-Ga2O3-based single crystal having a large outer diameter, a temperature difference between the center portion and the outer portion is reduced and the center portion is not solidified easily.